Manufacture of bodies from metal powder



7 April ,1929. c. F. SHERWOOD 1,708,192

MANUFACTURE OF BODIES FROM METAL POWDER Filed May '7, 1927 gwumtox M fmTES'

PATENT o 1,708,192 Fries.

CHARLES FREDERIO SHERWOOD, OF DETROIT, MICHIGAN.

IMANUFACTURE OF BODIES FROM METAL POWDER.

Application filed May 7,

This invention relates to the manufacture of bodies by compressing andsintering serlq block 12.

finely divided substances including finely divided metals, andparticularly to the manufacture of electrically. .conducting bOClIQSsuch as brushes for dyhamo electric machines.

One of the objects of the present invention 'is 'to provide an integralstructure comprising a body of sintered powdered materials includingpowedered metals and a previously formed rod or wire extendingtherefrom, the structure being such that the metal of said body mergesdirectly into the metal of the rod without any intermediate bond. Inrespect to the application of this inventlon to the manufacture ofelectrical brushes, it is an object to provide a brush of sintered metaland, integral therewith, a flexible conductor or pigtail. Furtherobjects and advantages of the present invention will be apparent fromthe following description, reference be1ng had to the accompanyingdrawings wherein a preferred embodiment of one form of the presentinvention is clearly shown.

In the drawings:

Fig. 1 is a side elevation, partly in vert cal section, showingapparatus for compressing powdered metals while at the same timeembedding into the compressed form the end of a flexible strandedconductor or pigtail.

Fig. 2 is a perspective view of the com- .pressed form with two flexibleconductors extending therefrom.

Fig. 3 is a longitudinal sectional new of a completed brush showing theconductors or pigtails permanently attached thereto. The sectional viewis-taken on the plane of line A- B of Fig. 2. r

In Fig. 1 of the drawings numeral 10 designates the bed plate of amolding press which supports a die 11 containing an 1n- The insert block12 supports two flexible strand conductors or pigtails 13, the upperends of which extend above the upper end of the insert block 12 asshpwn. The die is filled with a predetermined quantity ,of a mixture 14:of metal powders and graphite or other suitable filler. A briquettingplunger or ram 15 compresses the powder 14 into a briquette of the sizedesired for a. brush. The formed body is shown in Fig. 2 in whichnumeral 13 designates the pigtails, the numeral 16 the brush body. Thisbody with the pigtails is im- 1927. Serial No. 189,697.

mersed in a bath of molten salts, preferably the salts of alkalinemetals for a time sufficient to sinter the metallic particles and toform a coherent mass. After sintering the body is quenched in water andis ready for grinding its commutator'engaging surface.

The present invention is not limited to any particular mixture ofpowdered materials; but, by way of example, I have found thatsatisfactory results may be obtained from a mixture of metalpowderscontaining,

by weight: 87 parts copper, 7 parts lead, 1 parts tin, 4 parts graphite.lhe sintering bath should be approximately 1400 F.,

and for this purpose I prefer to use a bath of sodium cyanide. However,it is possible to use other salts or salt mixtures having approximatelythis melting point provided the salts do not materially affect the bodyto be sintered during the time of immersion of the body in the saltbath. The sintering time will of course depend ,on the-size of the bodyto be sintered. I have found that, for a small brush such as used inelectric motors for starting the internal combustion cordance with thepresent invention, this.

section being shown approximately or diagrammatically in Fig. 3, thatthe ends of pigtails: 13 which were embedded in the brush body 16 havecompletely lost their identity and have merged with the metal of thebrush to form an integral structure including the brush body and thepigtails. I have found that it is not necessary to fray out the ends ofthe pigtails which are embedded in the briquetted metal powder form inorder to provide means for anchoring the ends of the pigtails in thebrush body. The pigtails 13 may be cut off at right angles to theirlength as shown in Fig. 1. What becomes of the end portions .of thepigtails during the sintering operation I cannot definitely state but Ipresume that these ends may alloy with some of the finely divided metalparticles contained in the brush body. It may be that the ends of thepigtails may alloy with the tin particles of the brush specified by wayof example and thus form a bronze included in the structure of the brushbody;

One important feature is the use of a sintake place. If any metallicoxides are present within the briquetted form, these oxides will bereduced in the bath.

Whilel have used the term bond it will be understood that there isnointervening bonding metal joining the pigtails and the brush body. Theunion OftllC pigtails and brush body isso perfect that carefulexamination does not reveal where one part begins and the other ends.

By eliminating a joint between the brush. body and the pigtail I havegreatly prolonged the life of the brush since there is no possibility ofcorrosion at the joint, as occurs especially when the joint is formed bysoldering. Furthermore, by providing an in- .tegralv structure, I haveprovided a body which has substantially the same electrical conductivitythroughout. In this respect my invention is superior to structureshaving a joint between the brush body and the pigtail which has greaterelectrical resistance than the body or the pigtail.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to. be understood thatother forms might be adopted, all com; ing within the scope of theclaims which follow.

What is claimed is as follows:

1. The method of making an integral structure including a body of unitedmetallic particles and a preformed metal body which consists incompressing powdered metallic particles with a portion of the preformedbody embedded in the compressed form, and in heating the whole at atemperature and for a time suflicient to cause the metallic particles tounite, and the embedded portion of the preformed body to unite with aport-ion of the metallic structure of the other body, the heating takingplace in a molten salt bath having a melting point between 1200 F. andi500 F. and

having a fiuxing action which dissolves the oxides on the metalparticles thereby facilitating their alloyage;

2. The method of making an integral I structure including a body ofunited metal lic particles andla preformed metal body which consists incompressing powdered metallic particles with a portion of the preformedbody embedded in the compressed form, and in immersing the whole in amolten salt bath having a-melting point be- .tween 1200 F. and 1500 F.and having a fluxing action on themetals being sintered,

the temperature of the bath and the time of immersion being sufiicientto cause the me-' tallicparticles to uniteand-the embedded portion ofthe preformed body to unite with a portion of the metallic structure ofthe other body.

3. The method of making-a dynamo brush having a preformed conductorintegral therewith which consists in compressing abouta portion of thepreformed conductor a mixture of powdered materials including powderedmetals, and in immersing the whole in. a bath of molten sodium cyanidemaintained at a temperature of about 1400 F., the time being sufiicientto cause the metallic particles to unite to form the brush body and theembedded portion'of the preformed conductor to unite with themetallicstructure of the brush body. 4. The method of making a dynamo brushhaving a preformed conductor integral therewith comprising: moldingpowdered metals inthe form of a brush with a portion of said preformedconductor molded in place therein, and then sintering said molded unitto form an integral structure in a bath of molten sodium salt having amelting point between 1200 F. to 1500 F. and having a fluxing action onthe metals being sintered.

In testimony whereof I hereto aflix' my signature.

